Through array contact structure of three-dimensional memory device

ABSTRACT

Embodiments of through array contact structures of a 3D memory device and fabricating method thereof are disclosed. The 3D NAND memory device includes an alternating layer stack disposed on a substrate. The alternating layer stack includes a first region including an alternating dielectric stack, and a second region including an alternating conductor/dielectric stack. The memory device further comprises a barrier structure extending vertically through the alternating layer stack to laterally separate the first region from the second region, and multiple through array contacts in the first region each extending vertically through the alternating dielectric stack. At least one through array contact is electrically connected with a peripheral circuit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to PCT/CN2018/077719 filed on Mar. 1,2018, which claims priorities to Chinese Patent Application No.201710135654.9 filed on Mar. 8, 2017, Chinese Patent Application No.201710135329.2 filed on Mar. 8, 2017, and U.S. patent application Ser.No. 16/046.843 filed on Jul. 26, 2018, the entire contents of which areincorporated herein by reference.

BACKGROUND

Embodiments of the present disclosure relate to three-dimensional (3D)memory devices and fabrication methods thereof.

Planar memory cells are scaled to smaller sizes by improving processtechnology, circuit design, programming algorithm, and fabricationprocess. However, as feature sizes of the memory cells approach a lowerlimit, planar process and fabrication techniques become challenging andcostly. As a result, memory density for planar memory cells approachesan upper limit.

A 3D memory architecture can address the density limitation in planarmemory cells. The 3D memory architecture includes a memory array andperipheral devices for controlling signals to and from the memory array.

BRIEF SUMMARY

Embodiments of through array contact (TAC) structures of 3D memorydevices and fabrication methods thereof are disclosed herein.

Disclosed is a three-dimensional (3D) NAND memory device including analternating layer stack disposed on a substrate. The alternating layerstack can include a first region including an alternating dielectricstack comprising a plurality of dielectric layer pairs, and a secondregion including an alternating conductor/dielectric stack comprising aplurality of conductor/dielectric layer pairs. The three-dimensional(3D) NAND memory device further includes a barrier structure extendingvertically through the alternating layer stack to laterally separate thefirst region from the second region, and a plurality of through arraycontacts in the first region each extending vertically through thealternating dielectric stack. At least one of the plurality of througharray contacts is electrically connected with at least one peripheralcircuit.

In some embodiments, the barrier structure comprises silicon oxide andsilicon nitride. Each of the plurality of dielectric layer pairscomprises a silicon oxide layer and a silicon nitride layer, and each ofthe plurality of conductor/dielectric layer pairs comprises a metallayer and a silicon oxide layer. A number of the plurality of dielectriclayer pairs is at least 32, and a number of the plurality ofconductor/dielectric layer pairs is a least 32.

The three-dimensional (3D) NAND memory device further includes aplurality of slit structures each extending vertically through thealternating conductor/dielectric stack and laterally along the word linedirection to divide the alternating conductor/dielectric stack into aplurality of memory fingers.

In some embodiments, the barrier structure laterally extends along theword line direction, and the first region is separated by the barrierstructure from the second region and sandwiched between two neighboringslit structures.

In some embodiments, the barrier structure laterally extends along a bitline direction that is different than the word line direction tolaterally separate the first region from the second region. The bit linedirection can be perpendicular to the word line direction.

In some embodiments, a width of the first region enclosed by the barrierstructure in the bit line direction is larger than a distance betweentwo neighboring slit structures. The first region enclosed by thebarrier structure is sandwiched between two top selective gate staircaseregions in the word line direction. At least top two layers of thealternating conductor/dielectric stack in each top selective gatestaircase region have a staircase structure.

The three-dimensional (3D) NAND memory device further includes at leastone conductive layer on the staircase structure in the top selectivegate staircase regions and configured to interconnect top select gatesthat are above the alternating conductor/dielectric stack in the secondregion and on both sides of first region enclosed by the barrierstructure in the word line direction. At least two first regionsenclosed by corresponding barrier structures, each first regionextending parallel along the bit line direction.

The three-dimensional (3D) NAND memory device further includes aplurality of barrier structures to enclose a plurality of first regionsfrom the second region, the plurality of first regions are aligned inthe bit line direction. Each of the plurality of first regions issandwiched between two neighboring slit structures in the bit linedirection. The plurality of first regions are aligned as at least twocolumns in the bit line direction. At least one silt structure that issandwiched by two neighboring barrier structures in the bit linedirection includes a gap and configured to interconnect word lines ofneighboring memory fingers.

In some embodiments, the first region is separated by the barrierstructure from a staircase structure on an edge of the alternatingconductor/dielectric layer stack along the bit line direction. Anopening of the barrier structure is at an edge of the alternating layerstack along the bit line direction. A width of the first region in thebit line direction is larger than a distance between two neighboringslit structures. A width of the first region in the bit line directionis less than a maximum distance between two neighboring slit structuresin the staircase structure on the edge of the alternating layer stackalong the bit line direction.

The three-dimensional (3D) NAND memory device further includes aplurality of dummy channel structures adjacent to the barrier structure,each dummy channel structure extending vertically through thealternating conductor/dielectric stack.

Another aspect of the present disclosure provides a method for forming athree-dimensional (3D) NAND memory device, comprising: forming, on asubstrate, an alternating dielectric stack comprising a plurality ofdielectric layer pairs, each of the plurality of dielectric layer pairscomprising a first dielectric layer and a second dielectric layerdifferent from the first dielectric layer; forming at least one barrierstructure each extending vertically through the alternating dielectricstack, wherein the at least one barrier structure separates thealternating dielectric stack into at least one first region enclosedlaterally by at least the barrier structure, and a second region;forming a plurality of slits, and replacing, through the slits, firstdielectric layers in the second portion of the alternating dielectricstack with conductor layers to form an alternating conductor/dielectricstack comprising a plurality of conductor/dielectric layer pairs;depositing a conductive material into the slits to form a plurality ofslit structures; and forming a plurality of through array contacts inthe first region, each through array contact extending verticallythrough the alternating dielectric stack, to electrically connect atleast one of the plurality of through array contacts to at least oneperipheral circuit.

The method further includes forming the at least one peripheral circuiton a base substrate; forming at least one interconnect structure toelectrically connect the at least one of the plurality of through arraycontacts to the at least one peripheral circuit; and forming anepitaxial substrate above the at least one peripheral circuit. Thesubstrate at least includes the base substrate and the epitaxialsubstrate.

The method further includes prior to forming the slits, forming aplurality of doped regions in the epitaxial substrate, so as to contacteach slit structure with a corresponding doped region; forming at leastone opening in the epitaxial substrate corresponding to the at least onefirst region to expose an interconnect structure to electronicallyconnect with the at least one peripheral circuit; and filling the atleast one opening with a dielectric material.

The method further includes forming the plurality of slit structureslaterally to extend along a word line direction to divide thealternating conductor/dielectric stack into a plurality of memoryfingers.

The method further includes forming two parallel barrier structureslaterally to extend along the word line direction, such that the firstregion is separated by the two parallel barrier structure from thesecond region and sandwiched between two neighboring slit structures.

The method further includes forming the barrier structure laterallyextending along a bit line direction that is different than the wordline direction to laterally separate the first region from the secondregion.

The method further includes forming the barrier structure to laterallyextend along the bit line direction that is perpendicular to the wordline direction.

The method further includes forming the barrier structure such that awidth in the bit line direction of the first region enclosed by thebarrier structure is larger than a distance between two neighboring slitstructures.

The method further includes forming a staircase structure in thealternating dielectric stack adjacent to the barrier structure.

The method further includes forming at least one conductive layer on thestaircase structure adjacent to the barrier structure to interconnecttop select gates that are above the alternating conductor/dielectricstack in the second region, and on both sides of first region enclosedby the barrier structure in the word line direction.

The method further includes forming at least two barrier structures toenclose at least two first regions extending parallel along the bit linedirection.

The method further includes forming a plurality of barrier structures toenclose a plurality of first regions from the second region, theplurality of first regions are aligned in the bit line direction, suchthat each of the plurality of first regions is sandwiched between twoneighboring slit structures in the bit line direction.

The method further includes forming the plurality of barrier structuressuch that the plurality of first regions enclosed by the plurality ofbarrier structures are aligned as at least two columns in the bit linedirection.

The method further includes forming a gap in the at least one siltstructure that is sandwiched by two neighboring barrier structures inthe bit line direction to for interconnect word lines of neighboringmemory fingers.

The method further includes forming the barrier structure to separatethe first region in the staircase structure at the edge of thealternating stack, wherein an opening of the barrier structure is at theedge of the alternating layer stack along a bit line direction that isdifferent than the word line direction.

The method further includes forming the barrier structure, such that awidth of the first region in the bit line direction is larger than adistance between two neighboring slit structures.

The method further includes forming the barrier structure, such that awidth of the first region in the bit line direction is less than amaximum distance between two neighboring slit structures in thestaircase structure.

The method further includes forming a plurality of dummy channelstructures adjacent to the barrier structure, each dummy channelstructure extending vertically through the alternatingconductor/dielectric stack.

Other aspects of the present disclosure can be understood by thoseskilled in the art in light of the description, the claims, and thedrawings of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and form a partof the specification, illustrate embodiments of the present disclosureand, together with the description, further serve to explain theprinciples of the present disclosure and to enable a person skilled inthe pertinent art to make and use the present disclosure.

FIG. 1 illustrates a schematic diagram of an exemplary 3D memory devicein a plan view, according to some embodiments of the present disclosure.

FIG. 2 illustrates a schematic enlarged plan view of a region of 3Dmemory device including an exemplary bit line through array contactregion, according to some embodiments of the present disclosure.

FIGS. 3A-3D illustrate schematic enlarged plan views of a region of 3Dmemory device including various exemplary word line through arraycontact regions, according to some embodiments of the presentdisclosure.

FIGS. 4A-4B illustrate schematic enlarged plan views of a region of 3Dmemory device including various exemplary staircase structure througharray contact regions, according to some embodiments of the presentdisclosure.

FIG. 5 illustrates a schematic cross-sectional view of an exemplary 3Dmemory device according to some embodiments of the present disclosure.

FIG. 6 is a flowchart of an exemplary method for forming a 3D memorydevice, according to some embodiments of the present disclosure.

Embodiments of the present disclosure will be described with referenceto the accompanying drawings.

DETAILED DESCRIPTION

Although specific configurations and arrangements are discussed, itshould be understood that this is done for illustrative purposes only. Aperson skilled in the pertinent art will recognize that otherconfigurations and arrangements can be used without departing from thespirit and scope of the present disclosure. It will be apparent to aperson skilled in the pertinent art that the present disclosure can alsobe employed in a variety of other applications.

It is noted that references in the specification to “one embodiment,”“an embodiment,” “an example embodiment,” “some embodiments,” etc.,indicate that the embodiment described may include a particular feature,structure, or characteristic, but every embodiment may not necessarilyinclude the particular feature, structure, or characteristic. Moreover,such phrases do not necessarily refer to the same embodiment. Further,when a particular feature, structure or characteristic is described inconnection with an embodiment, it would be within the knowledge of aperson skilled in the pertinent art to effect such feature, structure orcharacteristic in connection with other embodiments whether or notexplicitly described.

In general, terminology may be understood at least in part from usage incontext. For example, the term “one or more” as used herein, dependingat least in part upon context, may be used to describe any feature,structure, or characteristic in a singular sense or may be used todescribe combinations of features, structures or characteristics in aplural sense. Similarly, terms, such as “a,” “an,” or “the,” again, maybe understood to convey a singular usage or to convey a plural usage,depending at least in part upon context.

It should be readily understood that the meaning of “on,” “above,” and“over” in the present disclosure should be interpreted in the broadestmanner such that “on” not only means “directly on” something but alsoincludes the meaning of “on” something with an intermediate feature or alayer therebetween, and that “above” or “over” not only means themeaning of “above” or “over” something but can also include the meaningit is “above” or “over” something with no intermediate feature or layertherebetween (i.e., directly on something).

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper,” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

As used herein, the term “substrate” refers to a material onto whichsubsequent material layers are added. The substrate itself can bepatterned. Materials added on top of the substrate can be patterned orcan remain unpatterned. Furthermore, the substrate can include a widearray of semiconductor materials, such as silicon, germanium, galliumarsenide, indium phosphide, etc. Alternatively, the substrate can bemade from an electrically non-conductive material, such as a glass, aplastic, or a sapphire wafer.

As used herein, the term “layer” refers to a material portion includinga region with a thickness. A layer can extend over the entirety of anunderlying or overlying structure, or may have an extent less than theextent of an underlying or overlying structure. Further, a layer can bea region of a homogeneous or inhomogeneous continuous structure that hasa thickness less than the thickness of the continuous structure. Forexample, a layer can be located between any pair of horizontal planesbetween, or at, a top surface and a bottom surface of the continuousstructure. A layer can extend horizontally, vertically, and/or along atapered surface. A substrate can be a layer, can include one or morelayers therein, and/or can have one or more layer thereupon, thereabove,and/or therebelow. A layer can include multiple layers. For example, aninterconnect layer can include one or more conductor and contact layers(in which contacts, interconnect lines, and/or vias are formed) and oneor more dielectric layers.

As used herein, the term “nominal/nominally” refers to a desired, ortarget, value of a characteristic or parameter for a component or aprocess operation, set during the design phase of a product or aprocess, together with a range of values above and/or below the desiredvalue. The range of values can be due to slight variations inmanufacturing processes or tolerances. As used herein, the term “about”indicates the value of a given quantity that can vary based on aparticular technology node associated with the subject semiconductordevice. Based on the particular technology node, the term “about” canindicate a value of a given quantity that varies within, for example,10-30% of the value (e.g., ±10%, ±20%, or ±30% of the value).

As used herein, the term “3D memory device” refers to a semiconductordevice with vertically-oriented strings of memory cell transistors(i.e., region herein as “memory strings,” such as NAND strings) on alaterally-oriented substrate so that the memory strings extend in thevertical direction with respect to the substrate. As used herein, theterm “vertical/vertically” means nominally perpendicular to a lateralsurface of a substrate.

Various embodiments in accordance with the present disclosure provide a3D memory device with through array contact (TAC) structures for amemory array (also referred to herein as an “array device”). The TACstructures allow contacts between the memory and various peripheralcircuits and/or peripheral devices (e.g., page buffers, latches,decoders, etc.) to be fabricated in a limited number of steps (e.g., ina single step or in two steps), thereby reducing the process complexityand manufacturing cost. The disclosed TACs are formed through a stack ofalternating dielectric layers, which can be more easily etched to formthrough holes therein compared with a stack of alternating conductor anddielectric layers.

The TACs can provide vertical interconnects between the stacked arraydevice and peripheral device (e.g., for power bus and metal routing),thereby reducing metal levels and shrinking die size. In someembodiments, the TACs can be interconnected with various lines in a topconductor layer and/or a bottom conductor layer, which are suitable forthose 3D memory architectures in which the array device and theperipheral device formed on different substrates are formed sequentiallyor joined by hybrid bonding in a face-to-face manner. In someembodiments, the TACs in the through array contact structures disclosedherein are formed through a stack of alternating dielectric layers,which can be more easily etched to form through holes therein comparedwith a stack of alternating conductor and dielectric layers, therebyreducing the process complexity and manufacturing cost.

FIG. 1 illustrates a schematic diagram of an exemplary 3D memory device100 in the plan view, according to some embodiments of the presentdisclosure. 3D memory device 100 can include a plurality of channelstructure regions (e.g., memory planes, memory blocks, memory fingers,etc., which are described in detail in connection with various figuresbelow), while one or more TAC structures can be formed between twoneighboring channel structure regions.

As shown in FIG. 1, 3D memory device 100 can include four or more memoryplanes 110, each of which can include a plurality of memory blocks 115.It is noted that, the arrangement of memory planes 110 in 3D memorydevice 100 and the arrangement of memory blocks 115 in each memory plane100 illustrated in FIG. 1 are only used as an example, which is notlimit the scope of the present disclosure.

TAC structures can include one or more bit line (BL) TAC regions 160that are sandwiched by two neighboring memory blocks 115 in the bit linedirection of the 3D memory device (labeled as “BL” in figures) andextended along the word line direction of the 3D memory device (labeledas “WL” in figures), one or more word line (BL) TAC regions 160 that aresandwiched by two neighboring memory blocks 115 in the word linedirection (WL) and extended along the bit line direction (BL), and oneor more staircase structure (SS) TAC regions 180 that are located at theedges of each memory plane 110.

In some embodiments, 3D memory device 100 can include a plurality ofcontact pads 120 arranged in a line at an edge of the 3D memory device100. Interconnect contact can be used for electrically interconnect 3Dmemory device 100 to any suitable device and/or interface that providedriving power, receive control signal, transmit response signal, etc.

FIG. 2 depicts an enlarged plan view of the region 130 shown in FIG. 1including an exemplary bit line (BL) TAC region 160 of the 3D memorydevice. FIGS. 3A-3D depict enlarged plan views of the region 140 shownin FIG. 1 including various exemplary word line (WL) TAC regions 170 ofthe 3D memory device. FIGS. 4A and 4B depict enlarged plan views of theregion 150 shown in FIG. 1 including various exemplary staircasestructure (SS) TAC regions 180 of the 3D memory device.

Referring to FIG. 2, an enlarged plan view of the region 130 shown inFIG. 1 including an exemplary bit line (BL) TAC region of the 3D memorydevice is illustrated according to some embodiments of the presentdisclosure. The region 200 of the 3D memory device (i.e., region 130 asshown in FIG. 1) can include two channel structure regions 210 (e.g.,neighboring memory blocks 115 in BL direction) and a bit line (BL) TACregion 233 (e.g., BL TAC region 160 as shown in FIG. 1).

Channel structure regions 210 can include an array of channel structures212, each is part of a NAND string including a plurality of stackedmemory cells. Channel structures 212 extend through a plurality ofconductor layer and dielectric layer pairs that are arranged along adirection that is perpendicular to the plan view, which is also referredas a direction that is perpendicular to the surface of the substrate ofthe 3D memory device, and/or a “vertical direction” (which isillustrated in a cross-sectional view in connection with FIG. 5described in detail below).

The plurality of conductor/dielectric layer pairs are also referred toherein as an “alternating conductor/dielectric stack.” The number of theconductor/dielectric layer pairs in alternating conductor/dielectricstack (e.g., 32, 64, or 96) can set the number of memory cells in 3Dmemory device 100. Conductor layers and dielectric layers in alternatingconductor/dielectric stack alternate in the vertical direction. In otherwords, except the ones at the top or bottom of alternatingconductor/dielectric stack, each conductor layer can be adjoined by twodielectric layers on both sides, and each dielectric layer can beadjoined by two conductor layers on both sides.

Conductor layers can include conductive materials including, but notlimited to, tungsten (W), cobalt (Co), copper (Cu), aluminum (Al),polycrystalline silicon (polysilicon), doped silicon, silicides, or anycombination thereof. Dielectric layers can include dielectric materialsincluding, but not limited to, silicon oxide, silicon nitride, siliconoxynitride, or any combination thereof. In some embodiments, conductorlayers include metal layers, such as W, and dielectric layers includesilicon oxide.

In some embodiments, BL TAC region 233 can be sandwiched by twoneighboring channel structure regions 210 in BL direction, and canextend in WL direction. TAC region 233 can be defined by a barrierstructure 224 in conjunction with the edges of BL TAC region 233 of the3D memory device. Multiple TACs 226 can be formed in BL TAC region 233,which is enclosed laterally by barrier structure 224 and the edges of BLTAC region 233. In some embodiments, multiple TACs 226 in BL TAC region233 can penetrate an alternating dielectric stack for switch routing andfor reducing bit line capacitance.

The alternating dielectric stack can include a plurality of dielectriclayer pairs that are arranged along the vertical direction that isperpendicular to the surface of the substrate of the 3D memory device(which is illustrated in a cross-sectional view in connection with FIG.5 described in detail below). Each dielectric layer pair includes afirst dielectric layer and a second dielectric layer that is differentfrom first dielectric layer. In some embodiments, first dielectric layerand second dielectric layer each includes silicon nitride and siliconoxide. First dielectric layers in alternating dielectric stack can bethe same as dielectric layers in the alternating conductor/dielectricstack described above. In some embodiments, the number of dielectriclayer pairs in the alternating dielectric stack is the same as thenumber of the conductor/dielectric layer pairs in the alternatingconductor/dielectric stack.

As shown in FIG. 2, each channel structure region 210 can include one ormore slit structures 214 each extending in WL direction. At least someslit structures 214 can function as the common source contact for anarray of channel structures 212 in channel structure regions 210. Slitstructures 214 can also divide the 3D memory device into multiple memoryfingers 242 and/or dummy memory fingers 246. A top select gate cut 255can be disposed in the middle of each memory finger 242 to divide thetop select gate (TSG) of the memory finger into two portions. The topselect gate cut 255 can include dielectric materials including, but notlimited to, silicon oxide, silicon nitride, silicon oxynitride, or anycombination thereof.

In some embodiments, dummy channel structures 222 are formed in part ofchannel structure regions 210, for example, in dummy memory fingers 246that are adjacent to BL TAC region 233 in BL direction. Dummy channelstructures 222 can provide mechanical support for the memory arraystructures. Dummy memory fingers 246 do not have memory functions, andthus bit lines and related interconnect lines are not formed in dummymemory fingers 246.

Referring to FIG. 3A, an enlarged plan view of the region 140 shown inFIG. 1 including an exemplary word line (WL) TAC region of the 3D memorydevice is illustrated according to some embodiments of the presentdisclosure. The region 300A of the 3D memory device (i.e., region 140 asshown in FIG. 1) can include channel structure regions 320, a word line(WL) TAC region 372 (e.g., WL TAC region 170 as shown in FIG. 1), andtop selective gate (TSG) staircase regions 330.

As shown in FIG. 3A, channel structure regions 320 can include an arrayof channel structures 312, each including a plurality of stacked memorycells. TSG staircase regions 330 can be disposed on the sides of channelstructure regions 320 and adjacent to WL TAC region 372 in the planview. That is, WL TAC region 372 is sandwiched by two TSG staircaseregions 330 in WL direction. WL TAC region 372 can be defined by abarrier structure 324. Multiple TACs 326 used for switch routing and forreducing word line capacitance can be formed in WL TAC region 372, whichis enclosed laterally by barrier structure 324.

In some embodiments, dummy channel structures 322 are formed outside WLTAC region 372 to provide mechanical support for the memory arraystructures. It is understood that dummy channel structures 322 can beformed in any regions outside WL TAC region 372, for example, in TSGstaircase regions 330, and along the edges of channel structure regions320 adjacent to TSG staircase regions 330. It is noted that, channelstructures 312 and dummy channel structures 322 penetrate thealternating conductor/dielectric stack, while TACs 326 penetrate thealternating dielectric stack.

In some embodiments, a plurality of slit structures 314 each extendingin WL direction can divide the 3D memory device into multiple memoryfingers 342, 344. At least some slit structures 314 can function as thecommon source contact for an array of channel structures 312 in channelstructure regions 320. Sidewalls of slit structures 314 can includedielectric materials including, but not limited to, silicon oxide,silicon nitride, silicon oxynitride, or any combination thereof. Fillingmaterial of slit structures 314 can include conductive materialsincluding, but not limited to, tungsten (W), cobalt (Co), copper (Cu),aluminum (Al), polycrystalline silicon (polysilicon), doped silicon,silicides, or any combination thereof.

A top select gate cut 355 can be disposed in the middle of each memoryfinger 342, 344 to divide the top select gate (TSG) of the memory fingerinto two portions. The top select gate cut 355 can include dielectricmaterials including, but not limited to, silicon oxide, silicon nitride,silicon oxynitride, or any combination thereof.

It is noted that, a width of WL TAC region 372 in BL direction can belarger than a width of each memory finger 342 or 344. That is, barrierstructure 324 in BL direction can cross at least two neighboring slitstructures 314. As such, the conductive layers in channel structureregions 320 in memory finger 344 can be completely blocked by barrierstructure 324. Therefore, the top selective gates of channel structures312 between two channel structure regions 320 in memory finger 344 onboth side of WL TAC region 372 are not interconnected by the topconductor layers in the alternating conductor/dielectric stack.

To interconnect the top selective gates of channel structures 312between two channel structure regions 320 in memory finger 344 on bothside of WL TAC region 372, TSG staircase regions 330 can include one ormore conductive lines (not shown in FIG. 3A) formed on a staircasestructure (e.g., within top two to four levels) for making electricalinterconnections with the top selective gates of channel structures 312between two channel structure regions 320 in memory finger 344 that areseparated by WL TAC region 372.

For example, slit structures 314 that are cut off by WL TAC region 372can extend into TSG staircase regions 330. The top two conductor layersin the alternating conductor/dielectric stack can have a single-sidestaircase structure. One or more interconnect layers with contacts canbe formed on the single-side staircase structure to provide electricalinterconnection between the top selective gates of channel structures312 in channel structure regions 320 and in memory finger 344 that areseparated by WL TAC region 372.

Accordingly, by introducing TSG staircase regions 330 that interconnectthe top selective gates on both sides of WL TAC region 372, WL TACregion 372 can extend along BL direction to provide an enough size toenclose a desired number of TACS 326. Further, each memory plane 110 asshown in FIG. 1 can include multiple WL TAC regions 372 arranged in WLdirection. That is, multiple memory blocks 115 can be arranged in WLdirection in each memory plane 110.

Referring to FIG. 3B, an enlarged plan view of the region 140 shown inFIG. 1 including another exemplary word line (WL) TAC region of the 3Dmemory device is illustrated according to some alternative embodimentsof the present disclosure. The region 300B of the 3D memory device(i.e., region 140 as shown in FIG. 1) can include channel structureregions 320, a dummy channel region 350 that encloses a word line (WL)TAC region 372 (e.g., WL TAC region 170 as shown in FIG. 1).

As shown in FIG. 3B, channel structure regions 320 can include an arrayof channel structures 312, each including a plurality of stacked memorycells. Dummy channel region 350 is sandwiched by two channel structureregions 320 in WL direction. WL TAC region 372 is enclosed by dummychannel region 350. WL TAC region 372 can be defined by a barrierstructure 324. Multiple TACs 326 can be formed in WL TAC region 372,which is enclosed laterally by barrier structure 324.

In some embodiments, dummy channel structures 322 are formed outside WLTAC region 372 to provide mechanical support for the memory arraystructures. It is understood that dummy channel structures 322 can beformed in any regions outside WL TAC region 372, for example, in dummychannel region 350, and along the edges of channel structure regions 320adjacent to dummy channel region 350. It is noted that, channelstructures 312 and dummy channel structures 322 penetrate thealternating conductor/dielectric stack, while TACs 326 penetrate thealternating dielectric stack.

In some embodiments, a plurality of slit structures 314 each extendingin WL direction can divide the 3D memory device into multiple memoryfingers 342, 344. A top select gate cut 355 can be disposed in themiddle of each memory finger 342, 344 to divide the top select gate(TSG) of the memory finger into two portions.

It is noted that, a width of WL TAC region 372 in BL direction can belarger than a width of each memory finger 342 or 344. That is, barrierstructure 324 in BL direction can cross at least two neighboring slitstructures 314. As such, the conductive layers in channel structureregions 320 in memory finger 344 can be completely blocked by barrierstructure 324. Therefore, the top selective gates of channel structures312 between two channel structure regions 320 in memory finger 344 onboth side of WL TAC region 372 are not interconnected by the topconductor layers in the alternating conductor/dielectric stack.

Because of that, in some embodiments associated with such design of WLTAC region 372, one memory plane 110 can include only two memory blocks115 in WL direction. WL TAC region 372 is sandwiched by the two memoryblocks (i.e., channel structure regions 320 as shown in FIG. 3B), whilethe outer sides of channel structure regions 320 in WL direction canhave a staircase structure (not shown in FIG. 3B). Thus, the topselective gates of channel structures 312 between two channel structureregions 320 in memory finger 344 on both side of WL TAC region 372 canbe interconnected by using the staircase structure on the edges of thememory plane 110 of the 3D NAND device. Such deign can be suitable forzigzag word line decoder (X-DEC) routing.

Referring to FIG. 3C, an enlarged plan view of the region 140 shown inFIG. 1 including other exemplary word line (WL) TAC regions of the 3Dmemory device is illustrated according to some alternative embodimentsof the present disclosure. The region 300C of the 3D memory device(i.e., region 140 as shown in FIG. 1) can include channel structureregions 320, a dummy channel region 350 that encloses a plurality ofword line (WL) TAC regions 376.

As shown in FIG. 3C, in some embodiments, a plurality of slit structures314 each extending in WL direction can divide the 3D memory device intomultiple memory fingers 342. A top select gate cut 355 can be disposedin the middle of each memory finger 342 to divide the top select gate(TSG) of the memory finger into two portions.

Channel structure regions 320 can include an array of channel structures312, each including a plurality of stacked memory cells. Dummy channelregion 350 is sandwiched by two channel structure regions 320 in WLdirection. A plurality of WL TAC regions 376 arranged in a column alongBL direction are enclosed by dummy channel region 350. Each WL TACregion 376 can be defined by a barrier structure 324. Multiple TACs 326can be formed in each WL TAC region 376, which is enclosed laterally bybarrier structure 324.

In some embodiment, a width of each WL TAC region 376 in BL directioncan be less than a width of each memory finger 342. That is, barrierstructure 324 of each WL TAC region 376 can be located between twoneighboring slit structures 314. Since barrier structure 324 of each WLTAC region 376 does not complete block the conductive layers in dummychannel region 350, the top selective gates of channel structures 312between two channel structure regions 320 in each memory finger 342 onboth side of WL TAC region 376 can be interconnected by the topconductor layers in the alternating conductor/dielectric stack in dummychannel region 350.

In some embodiments, dummy channel structures 322 are formed outside WLTAC region 376 to provide mechanical support for the memory arraystructures. It is understood that dummy channel structures 322 can beformed in any regions outside WL TAC region 376, for example, in dummychannel region 350, and along the edges of channel structure regions 320adjacent to dummy channel region 350. It is noted that, channelstructures 312 and dummy channel structures 322 penetrate thealternating conductor/dielectric stack, while TACs 326 penetrate thealternating dielectric stack.

Accordingly, by disposing one WL TAC region 376 within each memoryfinger 342, the top conductor layers in the alternatingconductor/dielectric stack may not be blocked by the WL TAC region 376.Thus, no additional structure is requested to further interconnect thetop selective gates of channel structures 312 between two channelstructure regions 320 in each memory finger 342 on both side of WL TACregion 376. Therefore, multiple WL TAC regions 376 can be arranged ineach memory finger 342 along WL direction. That is, a memory 110 caninclude multiple memory blocks 115 in WL direction.

Referring to FIG. 3D, an enlarged plan view of the region 140 shown inFIG. 1 including other exemplary word line (WL) TAC regions of the 3Dmemory device is illustrated according to some alternative embodimentsof the present disclosure. The region 300D of the 3D memory device(i.e., region 140 as shown in FIG. 1) can include channel structureregions 320, a dummy channel region 350 that encloses a plurality ofword line (WL) TAC regions 376.

As shown in FIG. 3D, in some embodiments, a plurality of slit structures314, 316 each extending in WL direction can divide the 3D memory deviceinto multiple memory fingers 342. In some embodiments, slit structures314 can extend in WL direction all the way in through two or morechannel structure regions 320 and one or more dummy channel regions 350.At least one silt structure 316 can include a gap 318 in a dummy channelregion 350, as shown in FIG. 3D. A top select gate cut 355 can bedisposed in the middle of each memory finger 342 to divide the topselect gate (TSG) of the memory finger into two portions.

Channel structure regions 320 can include an array of channel structures312, each including a plurality of stacked memory cells. Dummy channelregion 350 is sandwiched by two channel structure regions 320 in WLdirection. A plurality of WL TAC regions 376 arranged in a column alongBL direction are enclosed by dummy channel region 350. Each WL TACregion 376 can be defined by a barrier structure 324. Multiple TACs 326can be formed in each WL TAC region 376, which is enclosed laterally bybarrier structure 324.

In some embodiment, a width of each WL TAC region 376 in BL directioncan be less than a width of each memory finger 342. That is, barrierstructure 324 of each WL TAC region 376 can be located between twoneighboring slit structures 314. Since barrier structure 324 of each WLTAC region 376 does not complete block the conductive layers in dummychannel region 350, the top selective gates of channel structures 312between two channel structure regions 320 in each memory finger 342 onboth side of WL TAC region 376 can be interconnected by the topconductor layers in the alternating conductor/dielectric stack in dummychannel region 350.

In some embodiments, dummy channel structures 322 are formed outside WLTAC region 376 to provide mechanical support for the memory arraystructures. It is understood that dummy channel structures 322 can beformed in any regions outside WL TAC region 376, for example, in dummychannel region 350, and along the edges of channel structure regions 320adjacent to Dummy channel region 350. It is noted that, channelstructures 312 and dummy channel structures 322 penetrate thealternating conductor/dielectric stack, while TACs 326 penetrate thealternating dielectric stack.

In some embodiments, one or more silt structure 316 can include a gap318 in a dummy channel region 350. The word lines in neighboring memoryfingers 342 can be interconnected by using conductive lines goingthrough the gap 318. For example, as shown in FIG. 3D, the slitstructures 314 that are at the edges of a memory block 115 can extend inWL direction all the way in through two or more channel structureregions 320 and one or more dummy channel regions 350, while siltstructures 316 inside of each memory block 115 can include one or moregaps 318 in corresponding dummy channel regions 350 respectively. Assuch, all the top select gates and/or word lines in the same memoryblock 115 can be interconnected without additional structures.

Accordingly, by disposing WL TAC region 376 within memory finger 342 andproviding gap 318 in silt structure 316, the top conductor layers in thealternating conductor/dielectric stack may not be blocked by the WL TACregion 376, and word lines in neighboring memory fingers 342 can beinterconnected. Therefore, multiple WL TAC regions 376 can be arrangedin each memory finger 342 along WL direction. That is, a memory 110 caninclude multiple memory blocks 115 in WL direction. Such structure canhave a high integration level and a simply layout that can be easilyfabricated.

Referring to FIG. 4A, an enlarged plan view of the region 150 shown inFIG. 1 including an exemplary staircase structure (SS) TAC region of the3D memory device is illustrated according to some embodiments of thepresent disclosure. The region 400A of the 3D memory device (i.e.,region 150 as shown in FIG. 1) can include channel structure regions420, a staircase region 410, and a staircase structure (SS) TAC regions482.

Channel structure region 420 can include an array of channel structures412, each including a plurality of stacked memory cells. Staircaseregion 410 can include a staircase structure and an array of word linecontacts 432 formed on the staircase structure. In some embodiments, SSTAC region 482 is in staircase region 410. SS TAC region 482 can bedefined by a barrier structure 424 alone or in conjunction with an edgeof staircase region 410 of the 3D memory device. Multiple TACs 426 canbe formed in SS TAC region 482, which is enclosed laterally by at leastbarrier structure 424.

As shown in FIG. 4A, in some embodiments, a plurality of slit structures414, 416 each extending in WL direction can divide the 3D memory deviceinto multiple memory fingers 442, 444. In some embodiments, slitstructures 414 can extend in WL direction into at least a portion ofstaircase region 410. At least some silt structures 416 can include oneor more gaps 418 in staircase region 410. A top select gate cut 455 canbe disposed in the middle of each memory finger 442, 444 to divide thetop select gate (TSG) of the memory finger into two portions.

In some embodiments, one or more silt structure 416 can include a gap418 in staircase region 410. Word line contacts 432 in neighboringmemory fingers 442 can be interconnected by using conductive lines goingthrough the gap 418. For example, as shown in FIG. 4A, the slitstructures 414 that are at the edges of a memory block 115 can extend inWL direction all the way in through channel structure region 420 andstaircase region 410, while silt structures 416 inside of each memoryblock 115 can include one or more gaps 418 in staircase region 410. Assuch, all word line contacts 432 in the same memory block 115 can beinterconnected without additional structures.

It is noted that, a width of SS TAC region 482 in BL direction can belarger than a width of each memory finger 442, 444. That is, barrierstructure 424 in BL direction can cross at least two neighboring slitstructures 414. Since SS TAC region 482 occupies the area of a portionof staircase region 410 that corresponds to memory fingers 444completely blocked by barrier structure 424, the staircase structure inSS TAC region 482 is used for forming TACs 426 rather than forming wordline contacts 432 for memory fingers 444. Therefore, the staircasestructure corresponding to memory fingers 444 on the other side ofmemory plane 110 (not shown in FIG. 4B) can be used to form word linecontacts 432 rather than SS TAC region 482.

Accordingly, in some embodiments associated with such design of SS TACregion 482, SS TAC regions 482 on both sides of memory plane 110 do notoverlap in WL direction. That is, one memory finger corresponds to atmaximum one SS TAC region 482. Such deign can be suitable for zigzagword line decoder (X-DEC) routing. Further, in some embodimentsassociated with designs of SS TAC region 482 as well as WL TAC region372 described above in connection with FIG. 3B, due to the same reason,SS TAC regions 482 and WL TAC regions 372 do not overlap in WLdirection. That is, one memory finger corresponds to either one SS TACregion 482 or one WL TAC regions 372 at maximum.

Referring to FIG. 4B, an enlarged plan view of the region 150 shown inFIG. 1 including other exemplary staircase structure (SS) TAC regions ofthe 3D memory device is illustrated according to some alternativeembodiments of the present disclosure. The region 400B of the 3D memorydevice (i.e., region 150 as shown in FIG. 1) can include channelstructure regions 420, a staircase region 410, and a plurality ofstaircase structure (SS) TAC regions 484.

Channel structure region 420 can include an array of channel structures412, each including a plurality of stacked memory cells. Staircaseregion 410 can include a staircase structure and an array of word linecontacts 432 formed on the staircase structure. In some embodiments, SSTAC regions 484 are in staircase region 410. Each SS TAC regions 484 canbe defined by a barrier structure 424 alone or in conjunction with anedge of staircase region 410 of the 3D memory device. Multiple TACs 426can be formed in SS TAC region 482, which is enclosed laterally by atleast barrier structure 424.

As shown in FIG. 4B, in some embodiments, a plurality of slit structures414 each extending in WL direction in channel structure regions 420 candivide the 3D memory device into multiple memory fingers 442. A topselect gate cut 455 can be disposed in the middle of each memory finger442 to divide the top select gate (TSG) of the memory finger into twoportions. In some embodiments, slit structures 414 can extend in WLdirection into at least a portion of staircase region 410. In someembodiments, staircase region 410 can further include multiple slitstructures 416 that are not aligned with slit structures 414 in WLdirection. That is, distances between neighboring slit structures instaircase region 410 can be non-uniform. Some neighboring slit structurepairs can have a first distance that is larger than a second distancebetween other neighboring slit structure pairs.

In some embodiments, each SS TAC region 484 can be located between theneighboring slit structure pair that have the first distance. That is, awidth of SS TAC region 484 in BL direction can be less than the firstdistance. As such, other than the space occupied by SS TAC region 484,staircase region 410 between such neighboring slit structure pair thathave the first distance can have extra space to form word line contacts432.

Referring to FIG. 5, a schematic cross-sectional view of an exemplary 3Dmemory device 500 is illustrated according to some embodiments of thepresent disclosure. 3D memory device 500 can be part of a non-monolithic3D memory device, in which components (e.g., the peripheral device andarray device) can be formed separately on different substrates. Forexample, 3D memory device 500 can be region 130, region 140, or region150 described above in connection with FIG. 1.

As shown in FIG. 5, 3D memory device 500 can include a substrate 570 andan array device above the substrate 570. It is noted that X and Y axesare added in FIG. 5 to further illustrate the spatial relationship ofthe components in 3D memory device 500. Substrate 570 includes twolateral surfaces (e.g., a top surface 572 and a bottom surface 574)extending laterally in the X direction (the lateral direction, e.g., WLdirection or BL direction).

As used herein, whether one component (e.g., a layer or a device) is“on,” “above,” or “below” another component (e.g., a layer or a device)of a semiconductor device (e.g., 3D memory device 500) is determinedrelative to the substrate of the semiconductor device (e.g., substrate570) in the Y direction (the vertical direction) when the substrate ispositioned in the lowest plane of the semiconductor device in the Ydirection. The cross-sectional view of the 3D memory device 500 shown inFIG. 5 is along a plane in BL direction and Y direction. The same notionfor describing spatial relationship is applied throughout the presentdisclosure.

Substrate 570 can be used for supporting the array device, and caninclude a circuit substrate 530 and an epitaxial substrate 540. Circuitsubstrate 530 can include a base substrate 510 and one or moreperipheral circuits (not shown in FIG. 5) formed above base substrate510. Base substrate 510 can include any suitable semiconductor materialthat can include silicon (e.g., monocrystalline silicon, polycrystallinesilicon), silicon germanium (SiGe), gallium arsenide (GaAs), germanium(Ge), silicon on insulator (SOI), germanium on insulator (GOI), or anysuitable combination thereof. In some embodiments, base substrate 510 isa thinned substrate (e.g., a semiconductor layer), which was thinned bygrinding, wet/dry etching, chemical mechanical polishing (CMP), or anycombination thereof.

The one or more peripheral circuits formed in circuit substrate 530 caninclude any suitable digital, analog, and/or mixed-signal peripheralcircuits used for facilitating the operation of 3D memory device 500,such as page buffers, decoders, and latches (not shown in FIG. 5). Insome embodiments, circuit substrate 530 can further include one or moreinterconnection structures 532 for electrically connecting the one ormore peripheral circuits to the array device above the substrate 570.The one or more interconnection structures 532 can include any suitableconductive structures including, but not limited to, contacts,single-layer/multi-layer vias, conductive layer(s), plugs, etc.

Epitaxial substrate 540 can be formed on the circuit substrate 530 byusing a deposition process including, but not limited to, chemical vapordeposition (CVD), physical vapor deposition (PVD), atomic layerdeposition (ALD), or any combination thereof. Epitaxial substrate 540can be a single layer substrate or a multi-layer substrate, for example,a monocrystalline single-layer substrate, a polycrystalline silicon(polysilicon) single-layer substrate, a polysilicon and metalmulti-layer substrate, etc. Further, one or more openings 542 can beformed in regions of epitaxial substrate 540 that correspond to one ormore through array contact (TAC) structures of the array device. Aplurality of TACs 526 can go through one or more openings 542 toelectronically connect with one or more interconnection structures 532in circuit substrate 530.

In some embodiments, 3D memory device 500 is a NAND Flash memory devicein which memory cells are provided in the form of an array of channelstructures (not shown in FIG. 5) extending in Y direction abovesubstrate 570. The array device can include a plurality of channelstructures that extend through an alternating conductor/dielectric stack580 including a plurality of conductor layer 580A and dielectric layer580B pairs. The number of the conductor/dielectric layer pairs inalternating conductor/dielectric stack 580 (e.g., 32, 64, or 96) can setthe number of memory cells in 3D memory device 500.

Conductor layers 580A and dielectric layers 580B in alternatingconductor/dielectric stack 580 alternate in Y direction. In other words,except the ones at the top or bottom of alternating conductor/dielectricstack 580, each conductor layer 580A can be adjoined by two dielectriclayers 580B on both sides, and each dielectric layer 580B can beadjoined by two conductor layers 580A on both sides. Conductor layers580A can each have the same thickness or have different thicknesses.Similarly, dielectric layers 580B can each have the same thickness orhave different thicknesses. Conductor layers 580A can include conductormaterials including, but not limited to, tungsten (W), cobalt (Co),copper (Cu), aluminum (Al), polycrystalline silicon (polysilicon), dopedsilicon, silicides, or any combination thereof. Dielectric layers 580Bcan include dielectric materials including, but not limited to, siliconoxide, silicon nitride, silicon oxynitride, or any combination thereof.In some embodiments, conductor layers 580A include metal layers, such asW, and dielectric layers 580B include silicon oxide.

In some embodiments, the array device further includes slit structures514. Each slit structure 514 can extend in the Y direction throughalternating conductor/dielectric stack 580. Slit structure 514 can alsoextend laterally (i.e., substantially parallel to the substrate) toseparate alternating conductor/dielectric stack 580 into multipleblocks. Slit structure 514 can include a slit filled with conductormaterials including, but not limited to, W, Co, Cu, Al, silicides, orany combination thereof. Slit structure 514 can further include adielectric layer with any suitable dielectric materials between thefilled conductor materials and alternating conductor/dielectric stack580 to electrically insulate the filled conductor materials fromsurrounding conductor layers 580A in alternating conductor/dielectricstack 580. As a result, slit structures 514 can separate 3D memorydevice 500 into multiple memory fingers (e.g., as shown in FIGS. 2,3A-3D, 4A-4B in the plan view).

In some embodiments, slit structure 514 functions as the source contactfor channel structures in the same memory finger that share the samearray common source. Slit structure 514 can thus be referred to as a“common source contact” of multiple channel structures. In someembodiments, epitaxial substrate 540 includes a doped region 544(including p-type or n-type dopants at a desired doping level), and thelower end of slit structure 514 is in contact with doped region 544 ofepitaxial substrate 540.

In some embodiments, an alternating dielectric stack 560 can be locatedin a region that is surrounded laterally by a barrier structure 516 onepitaxial substrate 540. Alternating dielectric stack 560 can include aplurality of dielectric layer pairs. For example, alternating dielectricstack 560 is formed by an alternating stack of a first dielectric layer560A and a second dielectric layer 560B that is different from firstdielectric layer 560A. In some embodiments, first dielectric layer 560Aincludes silicon nitride and second dielectric layer 560B includessilicon oxide. Second dielectric layers 560B in alternating dielectricstack 560 can be the same as dielectric layers 580B in alternatingconductor/dielectric stack 580. In some embodiments, the number ofdielectric layer pairs in alternating dielectric stack 560 is the sameas the number of conductor/dielectric layer pairs in alternatingconductor/dielectric stack 580.

In some embodiments, barrier structure 516 extending in the Y directionto separate laterally alternating conductor/dielectric stack 580 andalternating dielectric stack 560. That is, barrier structure 516 canbecome the boundary between alternating conductor/dielectric stack 580and alternating dielectric stack 560. Alternating dielectric stack 560can be enclosed laterally by at least barrier structure 516. In someembodiments, barrier structure 516 is in a closed shape (e.g., arectangle, a square, a circle, etc.) in the plan view to completelyenclose alternating dielectric stack 560. For example, as shown in FIGS.3A-3D, barrier structures 324 are in a rectangle shape in the plan viewto completely enclose the alternating dielectric stack in WL TAC regions372, 376. In some embodiments, barrier structure 516 is not in a closedshape in the plan view, but can enclose alternating dielectric stack 560in conjunction with one or more edges of array device. For example, asshown in FIGS. 4A and 4B, barrier structure 424, in conjunction with theedge(s) of the 3D memory device, encloses the alternating dielectricstack in SS TAC regions 482, 484.

As shown in FIG. 5, 3D memory device 500 further includes a plurality ofTACs 526 each extending in Y direction through alternating dielectricstack 560. TACs 526 can be formed only inside the area enclosedlaterally by at least barrier structure 516, which includes a pluralityof dielectric layer pairs. That is, TACs 526 can extend verticallythrough dielectric layers (e.g., first dielectric layers 560S and seconddielectric layers 560B), but not through any conductor layers (e.g.,conductor layers 580A). Each TAC 526 can extend through the entirethickness of alternating dielectric stack 560, (e.g., all the dielectriclayer pairs in Y direction). In some embodiments, TAC 526 furtherpenetrate epitaxial substrate 540 through opening 542 and electricallycontact interconnection structure 532.

TACs 526 can carry electrical signals from and/or to 3D memory device500, such as part of the power bus, with shorten interconnect routing.In some embodiments, TACs 526 can provide electrical connections betweenthe array device and the peripheral devices (not shown in FIG. 5)through one or more interconnection structure 532. TACs 526 can alsoprovide mechanical support to alternating dielectric stack 560. Each TAC526 can include a vertical opening through alternating dielectric stack560 and that is filled with conductor materials, including, but notlimited to, W, Co, Cu, Al, doped silicon, silicides, or any combinationthereof. In some embodiments, as TACs 526 are formed in alternatingdielectric stack 560 (surrounding by dielectric layers), an additionaldielectric layer between TAC 526 and alternating dielectric stack 560 isnot needed for insulation purposes.

Referring to FIG. 6, a schematic flowchart of an exemplary method 600for forming a 3D memory device is illustrated according to someembodiments of the present disclosure. It should be understood that theoperations shown in method 600 are not exhaustive and that otheroperations can be performed as well before, after, or between any of theillustrated operations.

Referring to FIG. 6, method 600 starts at operation 602, in which asubstrate is formed. In some embodiments, forming the substrate canincluding forming a base substrate, forming at least one peripheralcircuit on the substrate, forming at least one interconnection structureelectronically contacting with the at least one peripheral circuit, andforming an epitaxial substrate on the at least one peripheral circuit.

The base substrate can be formed by using any suitable semiconductormaterial that can include silicon (e.g., monocrystalline silicon,polycrystalline silicon), silicon germanium (SiGe), gallium arsenide(GaAs), germanium (Ge), silicon on insulator (SOI), germanium oninsulator (GOI), or any suitable combination thereof. In someembodiments, forming the base substrate includes a thinning processincluding grinding, wet/dry etching, chemical mechanical polishing(CMP), or any combination thereof.

The one or more peripheral circuits can include any suitable digital,analog, and/or mixed-signal peripheral circuits including, but notlimited to, page buffers, decoders, and latches. In some embodiments,the one or more interconnection structures can include any suitableconductive structures including, but not limited to, contacts,single-layer/multi-layer vias, conductive layer(s), plugs, etc.

Epitaxial substrate can be formed above the one or more peripheralcircuits by using a deposition process including, but not limited to,chemical vapor deposition (CVD), physical vapor deposition (PVD), atomiclayer deposition (ALD), or any combination thereof. Epitaxial substratecan be a single layer substrate or a multi-layer substrate, for example,a monocrystalline single-layer substrate, a polycrystalline silicon(polysilicon) single-layer substrate, a polysilicon and metalmulti-layer substrate, etc.

In some embodiments, forming the epitaxial substrate further includesforming one or more openings such that at least part of the one or moreinterconnection structures are exposed by the one or more openings. Theone or more openings can corresponding to one or more through arraycontact TAC structures (e.g., word line (WL) TAC structure as shown inFIG. 2, bit line (BL) TAC structures as shown in FIGS. 3A-3D, andstaircase structure (SS) TAC structures as shown in FIGS. 4A-4B) formedin subsequence processes. The one or more openings can be filled withdielectric materials.

Method 600 proceeds to operation 604, in which an alternating dielectricstack is formed on the substrate. In some embodiments, a plurality offirst dielectric layer and second dielectric layer pairs can be formedon substrate to form alternating dielectric stack. In some embodiments,each dielectric layer pair includes a layer of silicon nitride and alayer of silicon oxide. Alternating dielectric stack can be formed byone or more thin film deposition processes including, but not limitedto, CVD, PVD, ALD, or any combination thereof.

Method 600 proceeds to operation 606, in which a staircase structure isformed at one or more edges of the alternating dielectric stack. In someembodiments, a trim-etch process can be performed on at least one side(in the lateral direction) of alternating dielectric stack to form thestaircase structure with multiple levels. Each level can include one ormore dielectric layer pairs with alternating first dielectric layer andsecond dielectric layer.

Method 600 proceeds to operation 608, a plurality of channel structuresand one or more barrier structures are formed. Each channel structureand each barrier structure can extend vertically through the alternatingdielectric stack.

In some embodiments, fabrication processes to form channel structureinclude forming a channel hole that extends vertically throughalternating dielectric stack by, for example, wet etching and/or dryetching. In some embodiments, fabrication processes to form channelstructure further include forming semiconductor channel and memory filmbetween semiconductor channel and the dielectric layer pairs inalternating dielectric stack. Semiconductor channel can includesemiconductor materials, such as polysilicon. Memory film can be acomposite dielectric layer, such as a combination of a tunneling layer,a storage layer, and a blocking layer.

The tunneling layer can include dielectric materials including, but notlimited to, silicon oxide, silicon nitride, silicon oxynitride, or anycombination thereof. Electrons or holes from the semiconductor channelcan tunnel to a storage layer through the tunneling layer. The storagelayer can include materials for storing charge for memory operation. Thestorage layer materials include, but are not limited to, siliconnitride, silicon oxynitride, a combination of silicon oxide and siliconnitride, or any combination thereof. The blocking layer can includedielectric materials including, but not limited to, silicon oxide or acombination of silicon oxide/silicon nitride/silicon oxide (ONO). Theblocking layer can further include a high-k dielectric layer, such as analuminum oxide (Al₂O₃) layer. Semiconductor channel and memory film canbe formed by one or more thin film deposition processes, such as ALD,CVD, PVD, any other suitable processes, or any combination thereof.

In some embodiments, fabrication processes to form barrier structure aresimilarly and simultaneously performed as the fabrication processes toform channel structure, thereby reducing fabrication complexity andcost. In some other embodiments, channel structure and barrier structureare formed in different fabrication steps so that barrier structure canbe filled with materials different from the materials filling channelstructure.

In some embodiments, fabrication processes to form a barrier structureinclude forming a trench that extends vertically through alternatingdielectric stack by, for example, wet etching and/or dry etching. Afterthe trench is formed through alternating dielectric stack, one or morethin film deposition processes can be performed to fill the trench withdielectric materials including, but not limited to, silicon oxide,silicon nitride, silicon oxynitride, silicon oxide/siliconnitride/silicon oxide (ONO), aluminum oxide (Al₂O₃), etc., or anycombination thereof.

By forming the one or more barrier structures, alternating dielectricstack can be separated into two types of regions: one or more insideregions each enclosed laterally by at least a barrier structure (inconjunction with the edge(s) of alternating dielectric stack in someembodiments) and an outside region in which channel structures and/orword line contacts can be formed. It is note that, each inside regioncorresponds to an opening in the epitaxial substrate.

In some embodiments, at least one inside region can be used to form a BLTAC structure as described above in connection with FIG. 2. As such, thebarrier structure enclosing such inside region can include two parallelbarrier walls that extend along WL direction.

In some embodiments, at least one inside region can be used to form a BLTAC structure as described above in connection with FIGS. 3A or 3B. Assuch, the barrier structure enclosing such inside region can have arectangular shape. A width of the barrier structure in BL direction canbe larger than a distance between two neighboring slit structures formedin subsequent processes.

In some embodiments, at least one inside region can be used to form a BLTAC structure as described above in connection with FIGS. 3C or 3D. Assuch, the barrier structure enclosing such inside region can have arectangular shape. A width of the barrier structure in BL direction canbe less than a distance between two neighboring slit structures formedin subsequent processes.

In some embodiments, at least one inside region can be used to form a SSTAC structure as described above in connection with FIG. 4A. As such,the barrier structure for separating such inside region can have arectangular shape with one open edge facing the edge of the staircasestructure. A width of the barrier structure in BL direction can belarger than a distance between two neighboring slit structures formed insubsequent processes.

In some embodiments, at least one inside region can be used to form a SSTAC structure as described above in connection with FIG. 4B. As such,the barrier structure for separating such inside region can have arectangular shape with one open edge facing the edge of the staircasestructure. A width of the barrier structure in BL direction can be lessthan a maximum distance between two neighboring slit structures formedin staircase region in subsequent processes.

In some embodiments, dummy channel structures can be formedsimultaneously with channel structures. The dummy channel structures canextend vertically through the alternating layer stack and can be filledwith the same materials as those in channel structures. Different fromchannel structures, contacts are not formed on the dummy channelstructures to provide electrical connections with other components ofthe 3D memory device. Thus, the dummy channel structures cannot be usedfor forming memory cells in the 3D memory device.

Method 600 proceeds to operation 610, in which a plurality of slits areformed, and first dielectric layers in a portion of the alternatingdielectric stack are replaced with conductor layers through theplurality of slits. For example, multiple parallel slit extending in WLdirection can be first formed by wet etching and/or dry etching ofdielectrics (e.g., silicon oxide and silicon nitride) throughalternating dielectric stack in the outside area. In some embodiments,doped regions are then formed in the epitaxial substrate under each slitby, for example, ion implantation and/or thermal diffusion through theslits. It is understood that doped regions can be formed in an earlierfabrication stage, for example, prior to the formation of the slits,according to some embodiments.

In some embodiments, the formed slits are used for the gate replacementprocess (also known as the “word line replacement” process) thatreplaces, in the outside area of alternating dielectric stack, firstdielectric layers (e.g., silicon nitride) with conductor layers (e.g.,W). It is noted that, the gate replacement occurs only in the outsidearea of alternating dielectric stack, but not in the inside area, due tothe formation of barrier structure. Barrier structure can prevent theetching of first dielectric layers (e.g., silicon nitride) in the insidearea of alternating dielectric stack because barrier structure is filledmaterials that cannot be etched by the etching step of the gatereplacement process.

As a result, after the gate replacement process, alternating dielectricstack in the outside region becomes alternating conductor/dielectricstack. The replacement of first dielectric layers with conductor layerscan be performed by wet etching first dielectric layers (e.g., siliconnitride) selective to second dielectric layers (e.g., silicon oxide) andfilling the structure with conductor layers (e.g., W). Conductor layerscan be filled by PVD, CVD, ALD, any other suitable process, or anycombination thereof. Conductor layers can include conductor materialsincluding, but not limited to, W, Co, Cu, Al, polysilicon, silicides, orany combination thereof.

Method 600 proceeds to operation 612, in which slit structures areformed by filling (e.g., depositing) conductor materials into the slitsby PVD, CVD, ALD, any other suitable process, or any combinationthereof. Slit structures can include conductor materials including, butnot limited to, W, Co, Cu, Al, polysilicon, silicides, or anycombination thereof. In some embodiments, a dielectric layer (e.g., asilicon oxide layer) is formed first between the conductor materials ofslit structure and conductor layers surrounding slit structure inalternating conductor/dielectric stack for insulation purposes. Thelower end of slit structure can be in contact with doped region.

Method 600 proceeds to operation 614, in which a plurality of TACs areformed through alternating dielectric stack. TACs can be formed in theone or more inside regions by first etching vertical openings (e.g., bywet etching and/or dry etching), followed by filling the openings withconductor materials using ALD, CVD, PVD, any other suitable processes,or any combination thereof. The conductor materials used for filling thelocal contacts can include, but are not limited to, W, Co, Cu, Al,polysilicon, silicides, or any combination thereof. In some embodiments,other conductor materials are also used to fill the openings to functionas a barrier layer, an adhesion layer, and/or a seed layer.

TACs can be formed by etching through the entire thickness ofalternating dielectric stack and the dielectric layer formed in theopening(s) in the epitaxial substrate. Because alternating dielectricstack includes alternating layers of dielectrics, such as silicon oxideand silicon nitride, the openings of TACs can be formed by deep etchingof dielectric materials (e.g., by deep reactive-ion etching (DRIE)process or any other suitable anisotropic etch process). In someembodiments, TACs penetrate the epitaxial substrate through openings ofthe epitaxial substrate. The lower end of TACs can be in contact withinterconnection structures in the substrate. As such, TACs can beelectrically connected with peripheral devices formed in the substrate.

In some embodiments, although TACs are formed after the gatereplacement, by reserving an area of alternating dielectric stack thatis not affected by the gate replacement process (not turned intoalternating conductor/dielectric stack), TACs are still formed throughdielectric layers (without passing through any conductor layers), whichsimplifies the fabrication process and reduces the cost.

Various embodiments in accordance with the present disclosure provide a3D memory device with through array contact structures for a memoryarray. The through array contact structures disclosed herein can includeTACs for providing vertical interconnects between the stacked arraydevice and peripheral device (e.g., for power bus and metal routing),thereby reducing metal levels and shrinking die size. In someembodiments, the TACs in the through array contact structures disclosedherein are formed through a stack of alternating dielectric layers,which can be more easily etched to form through holes therein comparedwith a stack of alternating conductor and dielectric layers, therebyreducing the process complexity and manufacturing cost.

Accordingly, one aspect of the present discloses a three-dimensional(3D) NAND memory device including a substrate including at least oneperipheral circuit, and an alternating layer stack disposed on thesubstrate. The alternating layer stack includes a first region includingan alternating dielectric stack including a plurality of dielectriclayer pairs, a second region including an alternatingconductor/dielectric stack including a plurality of conductor/dielectriclayer pairs, and a third region including staircase structures on edgesof the alternating conductor/dielectric layer stack in a word linedirection. The memory device further includes a barrier structureextending vertically through the alternating layer stack to laterallyseparate the first region from the second region or the third region, aplurality of channel structures and a plurality of slit structures eachextending vertically through the alternating conductor/dielectric stack,and a plurality of through array contacts in the first region eachextending vertically through the alternating dielectric stack. At leastone of the plurality of through array contacts is electrically connectedwith the at least one peripheral circuit.

Another aspect of the present disclosure provides a method for forming athree-dimensional (3D) NAND memory device. The method includes forming asubstrate including at least one peripheral circuit; forming, on thesubstrate, an alternating dielectric stack including a plurality ofdielectric layer pairs, each of the plurality of dielectric layer pairsincluding a first dielectric layer and a second dielectric layerdifferent from the first dielectric layer; forming a staircase structureat an edge of the alternating dielectric stack; forming a plurality ofchannel structures and at least one barrier structure each extendingvertically through the alternating dielectric stack. The at least onebarrier structure separates the alternating dielectric stack into atleast one first region enclosed laterally by at least the barrierstructure, and a second region. The method further comprises forming aplurality of slits, and replacing, through the slits, first dielectriclayers in the second portion of the alternating dielectric stack withconductor layers to form an alternating conductor/dielectric stackincluding a plurality of conductor/dielectric layer pairs; depositing aconductive material into the slits to form a plurality of slitstructures; and forming a plurality of through array contacts in thefirst region, each through array contact extending vertically throughthe alternating dielectric stack, to electrically connect at least oneof the plurality of through array contacts to the at least oneperipheral circuit.

The foregoing description of the specific embodiments will so fullyreveal the general nature of the present disclosure that others can, byapplying knowledge within the skill of the art, readily modify and/oradapt for various applications such specific embodiments, without undueexperimentation, without departing from the general concept of thepresent disclosure. Therefore, such adaptations and modifications areintended to be within the meaning and range of equivalents of thedisclosed embodiments, based on the teaching and guidance presentedherein. It is to be understood that the phraseology or terminologyherein is for the purpose of description and not of limitation, suchthat the terminology or phraseology of the present specification is tobe interpreted by the skilled artisan in light of the teachings andguidance.

Embodiments of the present disclosure have been described above with theaid of functional building blocks illustrating the implementation ofspecified functions and relationships thereof. The boundaries of thesefunctional building blocks have been arbitrarily defined herein for theconvenience of the description. Alternate boundaries can be defined solong as the specified functions and relationships thereof areappropriately performed.

The Summary and Abstract sections may set forth one or more but not allexemplary embodiments of the present disclosure as contemplated by theinventor(s), and thus, are not intended to limit the present disclosureand the appended claims in any way.

The breadth and scope of the present disclosure should not be limited byany of the above-described exemplary embodiments, but should be definedonly in accordance with the following claims and their equivalents.

What is claimed is:
 1. A three-dimensional (3D) memory device,comprising: an alternating dielectric stack comprising a plurality ofdielectric layer pairs arranged in a vertical direction; an alternatingconductor/dielectric stack comprising a plurality ofconductor/dielectric layer pairs arranged in the vertical direction; abarrier structure located between the alternating dielectric stack andthe alternating conductor/dielectric stack in a lateral direction; andat least one through array contact extending through the alternatingdielectric stack in the vertically direction and electrically connectingto a peripheral circuit.
 2. The memory device of claim 1, furthercomprises: a plurality of channel structures extending through thealternating conductor/dielectric stack in the vertically direction. 3.The memory device of claim 2, further comprising: a plurality of dummychannel structures each extending vertically through the alternatingconductor/dielectric stack, wherein the plurality of dummy channelstructures are located between the plurality of channel structures andthe barrier structure.
 4. The memory device of claim 1, wherein thebarrier structure comprises silicon oxide and silicon nitride.
 5. Thememory device of claim 1, wherein: each dielectric layer pair comprisesa silicon oxide layer and a silicon nitride layer; and eachconductor/dielectric layer pair comprises a metal layer and a siliconoxide layer.
 6. The memory device of claim 1, wherein: a number of theplurality of dielectric layer pairs is at least 32; and a number of theplurality of conductor/dielectric layer pairs is a least
 32. 7. Thememory device of claim 1, wherein: the barrier structure laterallyextends along a bit line direction to laterally separate the alternatingdielectric stack from the alternating conductor/dielectric stack.
 8. Thememory device of claim 1, wherein: the barrier structure laterallyencloses the alternating dielectric stack, and is laterally enclosed bythe alternating conductor/dielectric stack.
 9. The memory device ofclaim 8, further comprising: a plurality of barrier structures eachlaterally enclosing a corresponding alternating dielectric stack;wherein the plurality of alternating dielectric stacks extend parallelalong a bit line direction.
 10. The memory device of claim 9, wherein:the plurality of alternating dielectric stacks are aligned as at leasttwo columns in the bit line direction.
 11. The memory device of claims8, further comprising: a plurality of slit structures each extendingvertically through the alternating conductor/dielectric stack andlaterally along a word line direction.
 12. The memory device of claim11, wherein: a width of the alternating dielectric stack in a bit linedirection is larger than a distance between two neighboring slitstructures.
 13. A method for forming a three-dimensional (3D) memorydevice, comprising: forming an alternating dielectric stack comprising aplurality of dielectric layer pairs, each dielectric layer paircomprising a first dielectric layer and a second dielectric layerdifferent from the first dielectric layer; forming a barrier structureextending vertically through the alternating dielectric stack and inlaterally in a word line direction to separates the alternatingdielectric stack into at least a first portion and a second portion;replacing the first dielectric layers in the second portion of thealternating dielectric stack with conductor layers to form analternating conductor/dielectric stack comprising a plurality ofconductor/dielectric layer pairs; and forming at least one through arraycontact extending vertically through the first portion of thealternating dielectric stack to electrically connect to a peripheralcircuit.
 14. The method claim 13, before replacing the first dielectriclayers in the second portion of the alternating dielectric stack withthe conductor layers, further comprises: forming a plurality of channelstructures each extending vertically through the second portion of thealternating dielectric stack.
 15. The method of claim 14, furthercomprising: forming a plurality of dummy channel structures eachextending vertically through the second portion of the alternatingdielectric stack, wherein the plurality of dummy channel structures arelocated between the plurality of channel structures and the barrierstructure.
 16. The method of claim 13, wherein forming the alternatingdielectric stack comprises: forming at least 32 dielectric layer pairsin the alternating dielectric.
 17. The method of claim 13, whereinforming the barrier structure comprises: forming the barrier structureto laterally enclose the first portion of the alternating dielectricstack.
 18. The method of claim 17, further comprising: forming aplurality of barrier structures each laterally enclosing a correspondingportions of the alternating dielectric stack; wherein the pluralityportions of the alternating dielectric stacks extend parallel along abit line direction.
 19. The method of claims 13, before replacing thefirst dielectric layers in the second portion of the alternatingdielectric stack with the conductor layers, further comprising: forminga plurality of slit each extending vertically through the secondportions of the alternating dielectric stack and laterally along a wordline direction; and depositing a conductive material into the pluralityof slits to form a plurality of slit structures.
 20. The method of claim19, wherein forming the barrier structure comprises: forming the barrierstructure extending along a bit line direction, such that a width of thefirst portion of the alternating dielectric stack in the bit linedirection is larger than a distance between two neighboring slitstructures.